Bobbin and sewing machine

ABSTRACT

A bobbin detachably installed into an inner hook of a sewing machine is disclosed. The bobbin includes a bobbin shaft; and a pair of flanges that are provided at both axial ends of the bobbin shaft. The bobbin shaft is cylindrical and includes a first opening and a second opening defined on axial ends thereof, the bobbin shaft being provided with a restriction member in a proximity of either of the first and the second opening to allow attachment of the bobbin to the inner hook through the first opening.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2010-270255, filed on Dec. 3, 2010, the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure relates to a bobbin being wound with bobbin thread and having a bobbin shaft and a pair of flanges provided on both axial ends of the bobbin shaft. The present disclosure also relates to a sewing machine provided with an inner hook for housing the bobbin detachably within it.

BACKGROUND

Bobbins typically used in household sewing machine require the user to check the direction in which the bobbin thread is wound around the bobbin shaft in order to install the bobbin into the inner hook of the sewing machine in the proper direction. The bobbin thread wound on the bobbin installed into the inner hook is passed through the tension generator provided in the inner hook and drawn toward the needle hole of the needle plate. Thus, in case the bobbin is installed in the inner hook in the wrong direction, appropriate tension is not applied to the bobbin thread when the bobbin thread is passed through the tension generator during the sewing operation. This breaks the tension balance of the needle thread and the bobbin thread, known as thread tension, and prevents formation of neat stitches.

To address such concerns, bobbins have been suggested in which the flange on one side of the bobbin is labeled “This side up” and the flange on the other side is labeled “This side down”. If the user installs the bobbin into the inner hook in the wrong direction, the label “this side down” is presented to prompt the user to install the bobbin in the proper direction.

The problem with such bobbins is that the user may forget to check the label when installing the bobbin into the inner hook. Further, because the label is printed in small characters, the user may have difficulties in reading the label. Thus, the above described approach still leaves the possibility of misinstallation of the bobbin into the inner hook.

SUMMARY

One object of the present disclosure is to provide a bobbin that may be installed in the proper direction with respect to the inner hook and a sewing machine provided with an inner hook that allows detachable installation of such bobbin.

In one aspect of the present disclosure, a bobbin detachably installed into an inner hook of a sewing machine is disclosed. The bobbin includes a bobbin shaft; and a pair of flanges that are provided at both axial ends of the bobbin shaft. The bobbin shaft is cylindrical and includes a first opening and a second opening defined on the axial ends thereof, the bobbin shaft being provided with a restriction member in a proximity of either of the first and the second opening to allow attachment of the bobbin to the inner hook through the first opening.

Other objects, features and advantages of the present disclosure will become clear upon reviewing the following description of the illustrative aspects with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a sewing machine according to a first embodiment of the present disclosure having a bobbin attached to a thread winding shaft;

FIG. 2A is a vertical cross sectional view featuring a thread winder in a normal sewing operation;

FIG. 2B is a vertical cross sectional view featuring the thread winder in winding operation;

FIG. 3 is an exploded perspective view of an inner hook;

FIG. 4A is a planar view of the inner hook shown with a bobbin;

FIG. 4B is a cross sectional view taken along line IVb-IVb of FIG. 4A showing the inner hook with the bobbin and a tensioning mechanism removed;

FIG. 5A is a planar view of the bobbin;

FIG. 5B is a vertical cross sectional view of the bobbin;

FIG. 5C is a bottom view of the bobbin;

FIG. 6 is a perspective view of a tip of the thread winding shaft shown with the bobbin;

FIGS. 7A to 7C illustrate a second embodiment and correspond to FIGS. 5A to 5C;

FIG. 8A illustrates a third embodiment and corresponds to FIG. 5B;

FIG. 8B is a front view of the tip of the thread winding shaft; and

FIGS. 9A and 9B correspond to FIGS. 4A and 4B.

DETAILED DESCRIPTION

With reference to FIGS. 1 to 6, a description will be given hereinafter on a first embodiment of the present disclosure implemented through a household electronic sewing machine.

FIG. 1 generally illustrates a sewing machine 11 as seen from the user facing the front side of the sewing machine 11. Description will be given hereinafter with an assumption that the direction in which the user/operator positions himself/herself to face the sewing machine 11 is the forward direction and the opposite side, naturally, is the rear direction. The front and rear direction will also be referred to as a Y-direction. Further, the direction in which a pillar 13 is located relative to the center of a bed 12 is assumed as the rightward direction and the opposite side, is assumed as the left direction. The left and right direction will also be referred to as the X direction.

The sewing machine 11 is primarily configured by the bed 12, the pillar 13, and an arm 14 that are structurally integral. The pillar 13 extends upward from the right end of the X directionally oriented bed 12. From the upper end of the pillar 13, the arm 14 extends leftward over the bed 12 and the left end extreme of the arm 14 terminates into a head 15. Below the head 15, a needle bar not shown having a sewing needle 16 and a presser foot 18 are provided. On the front face of the arm 14, various operation switches such as a start/stop switch 19 for starting and stopping a sewing operation and a liquid crystal display 20 configured as a touch panel are provided.

On the upper surface of the bed 12, a needle plate 21 is provided. Though not shown in detail, the needle plate 21 has a needle hole allowing passage of sewing needle and a plurality of square holes allowing protruding and retracting of a feed dog 22 for feeding a workpiece. Inside the bed 12 below the needle plate 21, components such as a horizontal hook mechanism and a feed dog driving mechanism not shown are provided. The horizontal hook mechanism forms seams in coordination with the sewing needle 16 and the feed dog driving mechanism drives the feed dog 22. The horizontal hook mechanism is provided with an inner hook 24 shown in FIG. 4A which allows detachable attachment of a bobbin 23 wound with a thread 10. The bed 12 further contains a laterally extending lower shaft not shown that drives components such as the horizontal hook mechanism and the feed dog drive mechanism.

Though not shown in detail, the needle plate 21 is provided with a bobbin slot 21 a for taking bobbin in and out of the horizontal hook mechanism. The bobbin slot 21 a is opened/closed by a needle plate lid 25 made of transparent synthetic resin which is detachably attached to the needle plate 21. The needle plate 21 is further provided with a bobbin thread cutter 21 b on the left side of the bobbin slot 21 a. The bobbin thread cutter 21 b is typically configured by an enclosed bottom groove not shown which continues to the peripheral edge of the bobbin slot 21 a and a blade not shown formed at the terminating end of the enclosed bottom groove.

On the upper surface of the arm 14, as shown in FIG. 1, a recess is provided which serves as a thread spool storage 27. The thread spool storage 27 is provided with a thread spool shaft 27 a which allows detachable attachment of a thread spool 26 serving as a source of the thread 10. Provided further on the upper surface of the arm 14 is a front-side thread engagement 28 a and a rear-side thread engagement 28 b that are located on the left side of the thread spool storage 27.

On the right end of the arm 14, a thread winder 30 provided with a thread winding shaft 29 is disposed on the right side of the thread spool storage 27. The thread winder 30 winds the thread 10 supplied from the thread spool 26 around the bobbin 23 attached to the thread winding shaft 29. In the first embodiment, the thread 10 wound around the bobbin 23 is referred to as a bobbin thread 10.

As partially shown in FIGS. 2A and 2B, the arm 14 contains a laterally extending a main shaft 31 for driving components such as the needle bar and a thread take-up lever not shown. Though not shown, a sewing machine motor is disposed at the inner bottom portion of the pillar 13. At the inner upper portion of the pillar 13, a timing pulley 32 is provided for driving the main shaft 31 in rotation. As can be seen in FIGS. 2A and 2B, a timing belt 33 is wound around the timing pulley 32 and the sewing machine motor.

The rotational drive force of the timing pulley 32 is transmitted to the main shaft 31 through a clutch mechanism 34. During a normal sewing operation, the thread winding shaft 29 is placed in a standby position displaced relatively leftward as shown in FIG. 2A, whereas during thread winding operation of the thread winder 30, the thread winding shaft 29 is placed in a winding position displaced relatively rightward as shown in FIG. 2B. During the thread winding operation, the timing pulley 32 and the main shaft 31 are disconnected by the clutch mechanism 34 to allow the rotation of the thread winding shaft 29.

More specifically, the timing pulley 32 has a cylindrical support 32 a provided integrally to its central portion. The cylindrical support 32 a is fitted rotatably to the right end side of the main shaft 31. On the outer periphery of the cylindrical support 32 a, a plurality of teeth 32 b is formed so as to extend in the axial/lateral direction. The axial location of the timing pulley 32 relative to the main shaft 31 is determined by a transmission pin 31 a and a stopper ring 31 b being secured to the main shaft 31 and being located on the left and right side of the timing pulley 32. Thus, the timing pulley 32 is supported rotatably relative to the main shaft 31 but unmovably in the axial direction of the main shaft 31.

The clutch mechanism 34 is provided with components such as a clutch member 35, the transmission pin 31 a secured to the main shaft 31, and a compression coil spring 36. The clutch member 35 is a laterally extending cylindrical member having a diametrically large flange 35 a on its left end. On the inner peripheral surface of the clutch member 35, a plurality of laterally extending grooves 35 b are formed that are splined with the teeth 32 b of the cylindrical support 32 a, thereby allowing the clutch member 35 to slide in the axial direction of the main shaft 31.

The flange 35 a of the clutch member 35 has a recess 35 c in which the transmission pin 31 a secured to the main shaft 31 is fitted to allow the main shaft 31 to rotate integrally with the clutch member 35. The clutch member 35 is constantly biased leftward in engagement with the transmission pin 31 a by the spring force of the compression coil spring 36 placed between itself and the timing pulley 32. When the thread winding shaft 29 is placed in the left side standby position shown in FIG. 2A, the thread winding shaft 29 is leftwardly distanced from the flange 35 a and the recess 35 c of the clutch member 35 is placed in engagement with the transmission pin 31 a. Thus, the rotational drive force of the timing pulley 32 is transmitted to the main shaft 31 to allow the main shaft 31 to rotate integrally with the timing pulley 32 in the direction of arrow A.

When the thread winding shaft 29 is placed in the right side winding position shown in FIG. 2B by user operation, the lower end of the thread winding shaft 29 pushes the flange 35 a rightward to move the clutch member 35 rightward. The movement of the clutch member 35 disengages the clutch member 35 from the transmission pin 31 a. As a result, the rotational drive force of the timing pulley 32 is no longer transmitted to the main shaft 31 but instead, is transmitted to the thread winding shaft 29 by way of a later described a rubber ring 38. Thus, the thread winding shaft 29 is rotated clockwise in plan view, that is, in the direction of arrow B. On the left side surface of the timing pulley 32, a ring-shaped a pressure contact surface 32 c comprising a multiplicity of small bumps are provided to rotate the rubber ring 38 without slipping.

On the right end of the main shaft 31, a hand pulley 39 for user operation is mounted which protrudes from the right sidewall of the pillar 13. The main shaft 31 is connected to the lower shaft by way of a belt conveyor mechanism to be rotated in synchronism with one another, meaning that the main shaft 31 rotates once as the lower shaft rotates once.

Next, a horizontal hook serving as the horizontal hook mechanism will be described with reference to FIGS. 3 to 4B. The horizontal hook mechanism comprises an outer hook not shown that rotates in the horizontal direction and the inner hook 24 that fits inside the outer hook. The inner hook 24 does not rotate with the outer hook because the tip of a later described a rotation restrictor 41 is placed in contact with a rotation stopper not shown secured to the bed 12.

The outer hook is typically made of synthetic resin and is provided with a beak as well known. Outer hook is driven in rotation by the rotation of the lower shaft which in turn rotates in synchronism with the main shaft 31. Thus, the outer hook rotates counterclockwise in plan view in synchronism with the up and down movement of the needle bar. The rotation of the outer hook causes a needle thread loop not shown formed below the needle hole by the sewing needle to be seized by the beak. The needle thread loop seized by the beak is passed over the outer side of the inner hook 24 by the rotation of the beak or the outer hook so as to be interlaced with the bobbin thread 10.

The inner hook 24 is typically made of synthetic resin and is generally shaped as a shallow, circular container. The inner hook 24 has a bobbin container 40 for installation of the bobbin 23. The bobbin container 40 is disposed below the bobbin slot 21 a of the needle plate 21. As shown in FIG. 4B, at the center of a bottom wall 40 b of the bobbin container 40, a shaft 40 a is provided which is inserted into a later described a through hole 51 c of the bobbin 23, thereby allowing the bobbin 23 to rotate around the shaft 40 a. The shaft 40 a is generally cylindrical and protrudes upward from the bottom wall 40 a of the bobbin container 40. The length of protrusion of the shaft 40 a from the bottom wall 40 a, represented as axial height L, is configured to be smaller than the axial length of the bobbin 23. The shaft 40 a is configured to establish a fitting engagement with a later described a lower opening 51 a of the bobbin 23. On the outer periphery of the inner hook 24, the rotation restrictor 41 is provided so as to be located on the forward side of the inner hook 24 to prevent the rotation of the inner hook 24. Further on the outer periphery of the inner hook 24, a notch 92 is provided so as to be located on the rearward side of the inner hook 24 to allow the passage of the sewing needle 16. One end of the notch 42 is curved into a protrusive thread guide 42 a.

The forward inner wall of the bobbin container 40 is partially caved diametrically outward to form a generally arch-shaped a mounting recess 43. The mounting recess 43 is provided with a tension generator 44 that applies tension to the bobbin thread 10. FIG. 4B provides a cross sectional view of the inner hook 24 with the tension generator 44 and the bobbin 23 removed for ease of explanation and better visibility.

As shown in FIG. 3, a pair of holes 43 a and 43 b is defined on portions of the outer periphery of the inner hook 24 that correspond to the mounting recess 43. The tension generator 44 comprises a thread tension plate 45 and a thread tension spring 46. The thread tension plate 45 is arc-shaped and conforms with the mounting recess 43. The thread tension spring 46 also being arc-shaped conforms with the outer periphery of the thread tension plate 45. The thread tension spring 46 is made of an elastically deformable leaf spring. The thread tension plate 95 has a through hole 45 c formed on its lower left portion which communicates with a groove 95 d running leftwardly downward from its central upper edge. Further, the thread tension plate 45 has screw holes 45 a and 45 b formed at its central portion and the right end portion respectively.

The thread tension spring 46 has screw holes 46 a and 46 b formed at its central portion and right end portion respectively and a stepped portion 46 c formed between screw holes 46 a and 96 b. The thread tension plate 45 and the thread tension spring 46 being placed one over the other is screw fastened within the mounting recess 43 by a pair of screws 47 a and 47 b. The screw 47 a is passed through holes 43 a and 46 a in the listed sequence and fastened to the screw hole 45 a. Likewise, the screw 47 b is passed through holes 43 b and 46 b in the listed sequence and fastened to the screw hole 45 b. As shown in FIG. 4A, the stepped portion 46 c of the thread tension spring 46 produces a small spacing between the thread tension plate 45 and the thread tension spring 46 at their central portion, in other words, the proximity of the opened edge of the groove 45 d, while their left end portions, in other words, the proximity of the insert hole 45 c are placed in intimate contact .

As shown in FIGS. 3 and 4A, the bobbin thread 10 drawn from the bobbin 23 is passed through the insert hole 45 c and between the thread tension plate 45 and the thread tension spring 46 and guided upward. At this instance, the bobbin thread 10 is lightly clamped between the elastically deformed thread tension spring 46 and the thread tension plate 45 and thus, resistance is applied to the bobbin thread 10 as it is being guided upward. The tension generator 44 is thus, configured to apply a predetermined appropriate tension on the bobbin thread 10.

The bobbin 23 is provided with a restrictive element that restricts the direction of attachment of the bobbin 23 to the thread winding shaft 29 of the thread winder 30 and to the bobbin container 40 of the inner hook 24. The restrictive element allows the bobbin 23 to be constantly installed into the bobbin container 40 in the proper direction such that winding direction of the bobbin thread 10 is always oriented in the same direction. The structure of the bobbin 23 inclusive of the restrictive element will be described in detail with reference to FIGS. 5A to 5C.

The bobbin 23 is made of transparent synthetic resin and is an integral structure including the bobbin shaft 51, a pair of flanges 52 and 53 provided at each of the two ends of the bobbin shaft 51 so as to oppose one another. The bobbin shaft 51 is a cylindrical sleeve opened on both ends and having a penetrating the through hole 51 c running in the direction indicated by a central axis 54. The through hole 51 c receives the shaft 40 a of the bobbin container 40. One end of the bobbin shaft 31, shown as the lower end in FIG. 5B, is identified as the lower opening 51 a, whereas the other end is identified as the upper opening 51 b.

The pair of flanges 52 and 53 are disc shaped and extend in the direction orthogonal to the central axis 54 of the bobbin shaft 51. As shown in FIG. 5B, the lower side flange will also be referred to as the lower flange 52 and the upper side flange will also be referred to as the upper flange 53 hereinafter. The flanges 52 and 53 are each provided with a threading hole 55. The thread 10 is passed through the threading hole 55 prior to winding the thread 10 around the bobbin shaft 51 of the bobbin 23. In case the thread 10 is wound using the later described the thread winder 30, the thread 10 need not be passed through the threading hole 55.

The bobbin shaft 51 has a protrusion 56 formed integrally on its inner surface that narrows the upper opening 51 b to prevent attachment of the bobbin 23 to the inner hook 24. The protrusion 56 is located at the upper end side of the bobbin shaft 51 and protrudes radially inward from the peripheral edge of the through hole 51 c. As shown in FIG. 5A, the protrusion 56 is a crescent rib protruding so as to narrow diameter D of the upper opening 51 b by ⅕ to ¼. Thus, the user's attempt to install the bobbin 23 into the inner hook 24 with the upper flange 53 facing downward will fail because the protrusion 56 contacts the shaft 40 a of the inner hook 24 to prevent the shaft 40 a to be inserted from the upper opening 51 b. In contrast, in case the lower flange 52 is faced downward, the shaft 40 a is inserted into the lower opening 51 a to establish a fitting engagement to allow the bobbin 23 to be installed into the inner hook 24. Thus, the protrusion 56 allows the installation of the bobbin 23 into the inner hook 24 only from one side, that is, the lower flange 52 side.

Stated differently, only one side of opening 51 b is narrowed by the protrusion 56 to restrict the direction of installation of the bobbin 23. The protrusion 56 provided on the upper side of the bobbin 23 also serves as an indicator to identify the direction of installation of the bobbin 23 into the inner hook 24.

The sewing machine 11 according to the first embodiment also restricts the direction of attachment of the bobbin 23 to the thread winding shaft 29 of the thread winder 30. Description will be given on the thread winder 30 based on FIG. 6 featuring the structure of the thread winding shaft 29 to which the bobbin 23 is attached.

As shown in FIGS. 1 and 2A, the thread winder 30 is primarily configured by the thread winding shaft 29, a swinging arm 60 that rotatably supports the thread winding shaft 29, and a bobbin presser 61 provided on the upper surface of the arm 14. The thread winding shaft 29 is provided, in addition to the aforementioned rubber ring 38, components such as a positioning cam member 62, a bobbin receiving base 63, and a bobbin retention spring 64.

The swinging arm 60 is an integral structure including a cylindrical sleeve 60 a in which the lower portion of the thread winding shaft 29 is rotatably inserted, and an arm not shown extending rearward from the upper end of the cylindrical sleeve 60 a. Though not shown, the arm is supported swingably relative to a base member secured to the sewing machine frame. The swinging of the arm causes the swinging arm 60 to move integrally with the thread winding shaft 29 between the earlier described standby position and the winding position as can be seen in FIGS. 2A and 2B.

On a portion of the thread winding shaft 29 protruding downward from the cylindrical sleeve 60 a, a cylindrical rubber ring holder 38 a is secured that holds the rubber ring 38 on its outer peripheral surface. The thread winding shaft 29 is further provided with a stop ring 65 secured immediately above the cylindrical sleeve 60 a. The thread winding shaft 29 having the cylindrical sleeve 60 a interposed between the stop ring 65 and the rubber ring holder 38 a is retained by the swinging arm 60 so as to be axially unmovable relative to the swinging arm 60.

The thread winding shaft 29 further has the positioning cam member 62 secured above the stop ring 65. Though not shown in detail, the positioning cam member 62 is generally cylindrical and is provided with a horizontal cam portion 62 a at its lower end. The cam portion 62 a is generally disc-shaped and is provided with two recesses 62 b and 62 c. The two recesses 62 b and 62 c are diametrically symmetrical, meaning that they are 180 degrees apart from one another. The base member has a cam contact plate 66 mounted on it at a position corresponding to the cam portion 62 a of the positioning cam member 62 as partially shown in FIGS. 2A and 2B. In case the thread winding shaft 29 is moved to the standby position as shown in FIG. 2A, either recess 62 b or 62 c of the cam portion 62 a is placed in engagement with the cam contact plate 66 to lock the thread winding shaft 29 unrotatably. In case the thread winding shaft 29 is moved to the winding position as shown in FIG. 2B, on the other hand, the cam portion 62 a is disengaged from the cam contact plate 66 to allow the rotation of the thread winding shaft 29. At the same time, the rubber ring 38 at the lower end of the thread winding shaft 29 is pressed in contact with the pressure contact surface 32 c of the timing pulley 32 to allow the rotation of the timing pulley 32 to be transmitted to the thread winding shaft 29.

The thread winding shaft 29 has the bobbin receiving base 63 placed on the upper portion of the positioning cam member 62. The bobbin receiving base 63 is disc shaped and is slightly larger in outer diameter compared to flanges 52 and 53 of the bobbin 23. As shown in FIG. 6, the bobbin receiving base 63 is provided with two thread guide grooves 63 a penetrating in the thickness direction or the vertical direction. Bach of the thread guide grooves 63 a starts from an opening provided on the outer periphery of the bobbin receiving base 63 and extend inward in a direction opposite the rotational direction of the thread winding shaft 29 indicated by arrow B in FIG. 2B. The two thread guide grooves 63 a are 180 degrees apart from each other, meaning that they are diametrically symmetric. Inside the bobbin receiving base 63, a cutter 63 b is provided at the distal end of each thread guide groove 63 a for cutting the thread 10 though only shown in FIGS. 2A and 2B.

The thread winding shaft 29 is made of synthetic resin for example, and its upper end serves as an attachment 67 for attaching the bobbin 23 from above. As shown in FIG. 6, a chamfered surface 67 a is provided at the upper end of the attachment 67. Further, the upper half of the attachment 67 is provided with a slit 67 b that extends downward from its upper end. Inside the attachment 67, the bobbin retention spring 64 is provided which partially protrudes from the attachment 67. On the outer periphery of the attachment 67, a step 68 taking crescent shape in top view is provided that is mated with the protrusion 56 of the bobbin 23. On one part of the outer periphery of the attachment 67, a flat plane 68 a extends upright from the step 68.

Thus, the bobbin 23 is attached to the attachment 67 so as to be placed on the bobbin receiving base 63 with the lower flange 52 facing downward. When the bobbin 23 is attached, the step 68 is located below the protrusion 56. Further, the attachment 67 is provided with the plane 68 a on the upper side of the step 68 and a second fitting section 68 b on the lower side of the step 68 which establishes a fitting engagement with the lower opening 51 a of the bobbin 23.

Thus, even if the user, by mistake, tries to attach the bobbin 23 onto the attachment 67 of the thread winding shaft 29 with the upper flange 53 facing downward, the protrusion 56 of the upper opening 51 b contacts the step 68 and prevents the attachment of the bobbin 23. In contrast, the user's attempt to attach the bobbin 23 with the lower flange 52 facing downward will allow the second fitting section 68 b to be inserted in fitting engagement with the lower opening 51 a without the step 68 contacting the protrusion 56, meaning that the bobbin 23 is successfully attached to the attachment 67 of the thread winding shaft 29. As described above, the protrusion 56 only allows the bobbin 23 to be attached to the thread winding shaft 29 from one side, that is, through the lower opening 51 a.

The bobbin presser 61 is located to the immediate right side of the bobbin 23 attached to the thread winding shaft 29 in the winding position as shown in FIG. 1. The bobbin presser 61 is configured to contact the outer peripheral surface of the thread 10 wound around the bobbin 23 when the bobbin 23 is almost fully wound with the predetermined amount of the thread 10. Responsively, the bobbin 23 and consequently the thread winding shaft 29 is moved relatively leftward by the pressure applied by the bobbin presser 61. Thus, the rubber ring 38 is moved leftward away from the pressure contact surface 32 c to disallow the transmission of rotation and bring the thread winding shaft 29 to a stop. The “fully wound” state mentioned earlier indicates the state in which the bobbin 23 is wound up to approximately 70 to 90% of its maximum capacity where the wound thread 10 stays within the bounds of the outer periphery of flanges 52 and 53.

Next, a description will be given on the working of the above described structure. When executing a sewing operation, the sewing machine 11 winds the bobbin 23 with the thread winder 30 such that the bobbin thread 10 is wound in a predetermined direction, in this case, leftwardly wound as indicated in FIG. 4A. Thus, a bare bobbin 23 needs to be wound with the bobbin thread 10 prior to the sewing operation. The following preparatory steps are carried out by the user while the sewing machine 11, or more specifically, the sewing machine motor is stopped.

As can be seen in FIGS. 1 and 2A, the thread winding shaft 29 is normally, and while the sewing operation is ongoing, placed in a standby position. When the thread winding shaft 29 is in the standby position, the user is to attach the bobbin 23 to the attachment 67 located at the upper portion of the thread winding shaft 29. At this instance, the user is to hold the bobbin 23 such that the lower flange 52 faces downward toward the attachment 67 as shown in FIG. 6 so that the attachment 67 is inserted into the bobbin 23 through the lower opening 51 a. The bobbin 23 is thus, attached to the bobbin receiving base 63 so as to be placed on it through the fitting engagement between the second fitting section 68 b of the attachment 67 and the lower opening 51 a. The bobbin 23, when attached, is secured to the thread winding shaft 29 by the engagement of its upper end with the bobbin retention spring 64.

Even in case the user, by mistake, tries to attach the bobbin 23 to the attachment 67 of the thread winding shaft 29 with the upper flange 53 facing downward, the protrusion 56 prevents the fitting engagement of upper opening 51 b with the second fitting section 68 b. In other words, the user's attempt to attach the bobbin 23 to the thread winding shaft 29 in the wrong direction, that is, from the upper opening 51 b will fail because the contact between the protrusion 56 and the step 68 of the attachment 67 keeps the bobbin 23 floating above the bobbin receiving base 63. Thus, the user will recognize the his/her mishandling of the bobbin orientation for certain and be prompted to reattach the bobbin 23 in the proper direction in which the lower opening 51 a free of the protrusion 56, in other words, the lower flange 52 faces downward.

Then, the user is to set the thread spool 26 into the thread spool recess 27 as shown in FIG. 1 and draw the tip of the thread 10 from the thread spool 26 and thread the tip through threading sections 28 a and 28 b in the listed sequence. After manually winding the thread 10 around the bobbin shaft 51 of the bobbin 23 for several times, the user is to pass the tip of the thread 10 through the thread guide groove 63 a of the bobbin receiving base 63. The tip of the thread 10 passed through the thread guide groove 63 a is cut by the cutter 63 b. At this instance, the tip of the cut thread 10 is lightly held between the underside of the lower flange 52 and the upper surface of the bobbin receiving base 63. After completing the preparatory steps described above, the user is to manually move the thread winding shaft 29 rightward to the winding position. As a result, the outer peripheral surface of the rubber ring 38 is pressed against the pressure contact surface 32 c and the clutch member 35 is moved rightward to disconnect the timing pulley 32 from the main shaft 31.

Then, the user is to turn ON the start/stop switch 19 to drive the sewing machine motor in rotation. As the rotational drive force is transmitted to the thread winding shaft 29 by way of the timing belt 33, the timing pulley 32, and the rubber ring 38, the bobbin 23 rotates integrally with the thread winding shaft 29 to execute the winding operation. The winding operation leftwardly winds the thread 10 around bobbin shaft 51 by rotating the bobbin 23 in the direction indicated by arrow B in FIG. 2. In the first embodiment, “leftwardly wound” means that when the tip of the wound bobbin thread 10 is pulled and unwound, the bobbin 23 rotates in the leftward/counterclockwise direction in plan view as indicated in FIG. 4A.

Then, as bobbin becomes almost fully wound, the bobbin thread 10 wound on the bobbin 23 starts to contact the bobbin presser 61. Further, as amount of the bobbin thread 10 wound on the bobbin 23 increases, the thread winding shaft 29 is gradually moved leftward. Ultimately, transmission of the rotational drive force of the timing pulley 32 to the thread winding shaft 29 is disallowed to bring the thread winding shaft 29 to a stop. Thereafter, the user is to turn OFF the start/stop switch 19 to stop the sewing machine motor and place the thread winding shaft 29 back to the standby position. Then, the user is to remove the bobbin 23 wound with the bobbin thread 10 from the thread winding shaft 29.

Next, the user is to carry out the following steps in setting the bobbin thread 10 to the inner hook 24.

The user is to remove the needle plate lid 25 from the needle plate 21 to expose the bobbin slot 21 a. Then, the user is to install the bobbin 23 into the bobbin container 40 of the inner hook 24 through the bobbin slot 21 a. At this instance, the user is to attach the bobbin 23 to the shaft 40 a of bobbin from the lower opening 51 a with the lower flange 52 of the bobbin 23 facing downward. The bobbin 23 is thus, installed into the bobbin container 40 through the fitting engagement of the shaft 40 a and the lower opening 51 a.

Even in case the user, by mistake, tries to attach the bobbin 23 to the shaft 40 a with the upper flange 53 facing downward, the protrusion 56 prevents the fitting engagement of the upper opening 51 b with the shaft 40 a. In other words, the user's attempt to attach the bobbin 23 to the inner hook 24 in the wrong direction, that is, from the upper opening 51 b will fail because the contact between the protrusion 56 and the shaft 40 a does not allow the bobbin 23 to be passed all the way down to the bottom wall 40 b of the bobbin container 40, thereby not allowing the needle plate lid 25 to be closed. Thus, the user will recognize the his/her mishandling of the bobbin orientation for certain and be prompted to reattach the bobbin 23 in the proper direction in which the lower opening 51 a free of the protrusion 56, in other words, the lower flange 52 faces downward.

Next, the user is to draw the tip of the bobbin thread 10 upward from the bobbin 23 properly installed into the inner hook 29. Then, the user is to pass the bobbin thread 10 into the opened end of the groove 45 d defined on the thread tension plate 45 and guide it along the edge of the bobbin slot 21 a toward the insert hole 45 c. As a result, the bobbin thread 10 extending from the insert hole 45 c is passed between the thread tension plate 45 and the thread tension spring 46 to be guided upward. Thereafter, the user is to pass the tip of the bobbin thread 10 through the enclosed bottom groove of the thread cutter 21 b and cut off the tip with the cutter.

The bobbin thread 10 is thus, threaded to the tension generator 44. Moreover, because the direction of attachment of the bobbin 23 to the inner hook 24 is restricted as was the case in the attachment to the thread winding shaft 29, the bobbin thread 10 will always be leftwardly wound as can be seen in FIG. 4A. Thus, proper optimized tension is applied to the bobbin thread 10 by the tension generator 44 during the sewing operation to enable formation of neat stitches.

As described above, the bobbin 23 is provided with the lower opening 51 a and the upper opening 51 b and according to the first embodiment, the protrusion 56 for only allowing the attachment of the bobbin 23 to the inner hook 24 from or through the lower opening 51 a is provided in the proximity of the upper opening 51 b. The protrusion 56 only allows attachment of the bobbin 23 to the inner hook 24 from one side of the bobbin 23, in this case, the lower opening 51 a side, to allow the bobbin 23 to be always installed in the proper direction. Thus, the user's attempt to install the bobbin 23 into the inner hook 24 in the wrong direction is restricted or rejected by the protrusion 56. Unlike the approach in which a label is merely provided on the bobbin, the protrusion 56 prevents misoriented installation of the bobbin 23 for certain.

The protrusion 56 is configured to prevent the attachment of the bobbin 23 from the upper opening 51 b by narrowing the upper opening 51 b. Thus, the user's attempt to attach bobbin 23 from the upper opening 51 b is prevented by the protrusion 56 provided in the proximity of the upper opening 51 b or the upper opening 51 b side. The above described configuration allows the direction of attachment of the bobbin 23 to be restricted more reliably.

By providing the protrusion 56 on the inner surface of the upper opening 51 b as described above, misoriented installation of the bobbin 23 can be prevented in a simple structure without having to increase the size of the bobbin 23. Because the protrusion 56 is contained within the bobbin shaft 51, the outer periphery of the bobbin 51 and flanges 52 and 53 need not be changed in shape. Stated differently, the protrusion 56 is added to a known bobbin. Thus, the same amount of bobbin thread can be wound on the bobbin 23 as compared to a conventional bobbin even in the presence of the protrusion 56.

The inner hook 24 of the sewing machine 11 is provided with the shaft 40 a which establishes a fitting engagement with the lower opening 51 a but not with the upper opening 51 b because of the presence of the protrusion 56. Accordingly, the protrusion 56 only allows attachment of the bobbin 23 to the inner hook 24 from only one side of the bobbin 23, in this case, the lower opening 51 a side to allow the bobbin 23 to be always installed in the proper orientation. Even in case the user tries to install a misoriented bobbin 23 into the inner hook 24, the protrusion 56 does not allow the fitting of the bobbin 23 with the shaft 40 a. Unlike the approach in which a label is merely provided on the bobbin, the protrusion 56 prevents misoriented installation of the bobbin 23 for certain. Thus, proper optimized tension is applied to the bobbin thread 10 during the sewing operation to enable formation of neat stitches.

The thread winding shaft 29 of the thread winder 30 is provided with the second fitting section 68 b which establishes a fitting engagement with the lower opening 51 a but not with the upper opening 51 b because of the presence of the protrusion 56. The presence of the protrusion 56 restricts the direction of attachment of bobbin to the second fitting section 68 b. Thus, the thread 10 will always be wound in the same particular direction around the bobbin 23 by the thread winder 30. In the above described sewing machine, because the direction of attachment of the bobbin 23 is restricted by both the inner hook 24 and the thread winder 30, the bobbin 23 can be attached to the inner hook 24 with the bobbin thread 10 always wound on the bobbin 23 in the same direction.

FIGS. 7A to 7C illustrate a second embodiment. The elements that are identical to those of the first embodiment are identified with identical reference symbols. The differences from the first embodiment will be given hereinafter.

A bobbin 23′ of the second embodiment differs from the bobbin 23 of the first embodiment in the following respects. The bobbin 23′ includes an upper opening 51 b′ that is integrally provided with a plurality of protrusions 56 and 56′ Protrusions 56 and 56′ are symmetrical with respect to a central axis 54 and are 180 degrees apart from one another. Thus, the upper opening 51 b′ of the second embodiment is narrowed by protrusions 56 and 56′ to exhibit an oval-like shape as shown in FIG. 7A.

Though not shown, the attachment 67 of the thread winding shaft 29 of the second embodiment is provided with two pairs of plane 68 a and step 68 each pair being mated with either of protrusions 56 and 56′. The two pairs of plane 68 a and step 68 are 180 degrees apart from each other. Thus, the user's attempt to attach the bobbin 23 to the thread winding shaft 29 with the upper opening 51 b′ facing downward will fail because the contact between protrusions 56 and 56′ of the upper opening 51 b′ with the upper end or steps 68 and 68′ of the attachment 67 restricts the attachment of the bobbin 23. In contrast, the bobbin 23′ can be successfully attached to the attachment 67 as was the case in the first embodiment if the bobbin 23 is oriented such that the lower flange 52 faces downward.

The user's attempt to attach the bobbin 23′ to the inner hook 24 with the upper flange 53 facing downward will similarly fail because protrusions 56 and 56′ contacts the shaft 40 a. In contrast, the bobbin 23′ can be successfully attached to the shaft 40 a as was the case in the first embodiment if the bobbin 23 is oriented such that the lower flange 52 faces downward. Further, in the second embodiment, protrusions 56 and 56′ are formed symmetrically on the peripheral edge of the upper opening 51 b′ with constant spacing therebetween, which is structurally advantageous in obtaining sufficient mechanical strength. As described above, the number of protrusions, the length, and the shape of the protrusion(s) may be modified according to the requirements of mechanical strength.

FIGS. 8A to 9B illustrate a third embodiment. The elements that are identical to those of the first embodiment are identified with identical reference symbols. The differences from the first embodiment will be given hereinafter.

A bobbin 70 of the third embodiment differs from the bobbin 23 of the first embodiment in the following respects. As shown in FIG. 8A, the bobbin 70 lacks the protrusion 56 provided in the bobbin 23 of the first embodiment and inner diameter of an upper opening 70 b has measurement D which is identical to the measurement of the through hole 51 c. On a lower opening 70 a side of the bobbin 70, a taper 71 is formed which restricts the attachment of the bobbin 70 to a thread winding shaft 72 or an inner hook 73 of the third embodiment through the lower opening 70 a only.

More specifically, the taper 71 being provided all around the perimeter of the lower opening 70 a spreads out toward its opening end. The opening end of the taper 71 shown as the lower end as viewed in FIG. 8A has diameter D1 which is greater than inner diameter D (D<D1) of the upper opening 70 b. The taper 71 is thus, inclined by predetermined angle α, example of which may be 45 degrees. Thus, the taper 71 is formed so as to widen the width of the lower opening 70 a.

As shown in FIG. 8B, an attachment 74 of the thread winding shaft 72 lacks the plane 68 a and the step 68 provided in the first embodiment but is provided with a second fitting section 74 a mating with the taper 71. The second fitting section 74 a being provided on the lower portion of the attachment 74 is inclined by angle α equal to the inclination angle of the taper 71 so as to increase its diameter toward its lower end. Further, axial length L1 of the second fitting section 74 a of the attachment 74 is configured to be equal to length L2 (L1=L2) of the taper 71 of the bobbin 70 taken along the central axis 54. Thus, the second fitting section 74 a is configured as a taper that fits with the taper 71 located in the lower opening 70 a side but does not fit with the upper opening 70 b.

As shown in FIG. 9B, the bottom wall 40 b of the inner hook 73 is provided with a trapezoidal cone 73 a instead of the shaft 40 a. The trapezoidal cone 73 a is configured to increase its diameter toward its lower end as was the case in the second fitting section 74 a. That is, inclination angle of the trapezoidal cone 73 a is set at angle α and its axial length L is configured to be equal to length L2 (L=L2) of the taper 71 taken along the central axis 54. Thus, the trapezoidal cone 73 a is configured as a taper that fits with the taper 71 located in the lower opening 70 a side but does not fit with the upper opening 70 b.

According to the above described configuration, when attaching the bobbin 70 to the thread winding shaft 72, the user is to insert the attachment 74 into the lower opening 70 a with the lower flange 52 of the bobbin 70 facing downward. The bobbin 70 is thus, attached to the bobbin receiving base 63 so as to be placed on it through the fitting engagement between the second fitting section 74 b of the attachment 74 and the taper 71 of the lower opening 70 a. Even in case the user, by mistake, tries to attach the bobbin 70 to the attachment 74 with the upper flange 53 facing downward, the upper opening 70 b will not fit with the second fitting section 79 a. In other words, the user's attempt to attach the bobbin 70 to the thread winding shaft 72 in the wrong direction, that is, from the upper opening 70 b will fail because the contact between the upper opening 70 b and the upper end 74 b of the second fitting section 74 a keeps the bobbin 70 floating above the bobbin receiving base 63. Thus, the user will recognize the his/her mishandling of the bobbin orientation for certain and be prompted to reattach the bobbin 70 in the proper direction in which the lower opening 70 a provided with the taper 71 faces downward.

When attaching the bobbin 70 to the inner hook 73, the user is to insert the trapezoidal cone 73 a of the bobbin container 40 into the lower opening 70 a with the lower flange 52 of the bobbin 70 facing downward. The bobbin 70 is thus, attached to the bobbin container 40 so as to be installed into it by the fitting engagement between the taper 71 and the trapezoidal cone 73 a. Even in case the user, by mistake, tries to attach the bobbin 70 to the trapezoidal cone 73 a with the upper flange 53 facing downward, the contact between the upper opening 70 b and the upper end of the trapezoidal cone 73 a disallows the fitting of the upper opening 70 b and the trapezoidal cone 73 a. In other words, the user's attempt to attach the bobbin 70 to the inner hook 73 in the wrong direction, that is, from the upper opening 70 b will fail because the contact between the upper opening 70 b and the trapezoidal cone 73 a does not allow the bobbin 70 to be passed all the way down to the bottom wall 40 b of the bobbin container 40, thereby not allowing the needle plate lid 25 to be closed. Thus, the user will recognize the his/her mishandling of the bobbin orientation for certain and be prompted to reattach the bobbin 70 in the proper direction in which the lower opening 70 a provided with the taper 71 faces downward.

As described above, the third embodiment is provided with taper 71 that relatively widens the width of lower opening 70 a of bobbin 70 to allow the attachment of bobbin 70. Thus, taper 71 allows the direction of attachment of bobbin 70 to be restricted more reliably.

The taper 71 is inclined to spread out toward its opening end. Thus, the direction of attachment of the bobbin 70 can be restricted by simply tapering the lower opening 70 a. Further, the outer periphery of bobbin 51 or flanges 52 and 53 need not be changed in shape. Stated differently, taper is added to a known bobbin. Thus, the third embodiment provides similar operation and effect to those of the first embodiment such as allowing the same amount of bobbin thread to be wound on the bobbin 70 as compared to a conventional bobbin.

The present disclosure is not limited to the foregoing embodiments described or shown but may be modified or expanded as follows.

The bobbins 23 and 70 may be modified in form such as eliminating the threading hole 55.

The taper 71 may replaced by any other structure that widens the lower opening relative to the upper opening. Though not shown, the taper 71 may be replaced by a stepped structure that is caved diametrically outward. By spreading out the outer edge of the lower opening concentrically by such stepped structure, the operation and effect similar to those of the third embodiment can be achieved. More than one of such stepped structure may be provided in a modified embodiment.

The above described bobbin is not limited to application to the household electronic sewing machine 11 but maybe applied to sewing machines in general that are provided with an inner hook allowing detachable attachment of such bobbin.

While various features have been described in conjunction with the examples outlined above, various alternatives, modifications, variations, and/or improvements of those features and/or examples may be possible. Accordingly, the examples, as set forth above, are intended to be illustrative. Various changes may be made without departing from the broad spirit and scope of the underlying principles. 

1. A bobbin detachably installed into an inner hook of a sewing machine comprising: a bobbin shaft; a pair of flanges that are provided at both axial ends of the bobbin shaft; wherein the bobbin shaft is cylindrical and includes a first opening and a second opening defined on the axial ends thereof, the bobbin shaft being provided with a restriction member in a proximity of either of the first and the second opening to allow attachment of the bobbin to the inner hook through the first opening.
 2. The bobbin according to claim 1, wherein the restriction member is provided in the proximity of the second opening such that the second opening is narrowed to inhibit attachment of the bobbin.
 3. The bobbin according to claim 2, wherein the restriction member is provided on an inner surface of the second opening and comprises one or more protrusions protruding so as to narrow the second opening.
 4. The bobbin according to claim 1, wherein the restriction member is provided on an inner surface of the first opening and comprises a spreading section that widens the first opening relative to the second opening to allow attachment of the bobbin to the inner hook.
 5. The bobbin according to claim 4, wherein the spreading section comprises a taper that is inclined to spread out toward an opening end thereof.
 6. A sewing machine comprising: an inner hook that detachably installs a bobbin provided with a bobbin shaft and a pair of flanges at both axial ends of the bobbin shaft; wherein the bobbin shaft is cylindrical and includes a first opening and a second opening defined on axial ends thereof, the bobbin shaft being provided with a restriction member in a proximity of either of the first and the second opening to allow attachment of the bobbin to the inner hook through the first opening, and wherein the inner hook is provided with a first fitting section that fits with the first opening and not with the second opening, the bobbin being attached to the inner hook only through the first opening by the fitting of the first fitting section and the first opening.
 7. The sewing machine according to claim 6, further comprising a thread winder that is provided with a thread winding shaft to which the bobbin is detachably attached and that winds the bobbin with a thread supplied from a thread spool by rotating the thread winding shaft, the thread winding shaft being provided with a second fitting section that fits with the first opening and not with the second opening, and the bobbin being attached to the thread winding shaft only through the first opening by the fitting of the second fitting section and the first opening. 